Shares of options exchange CBOE Holdings are rising in their trading debut.

CBOE Holdings Inc.'s initial public offering of 11.7 million shares priced at $29 per share, the top of the expected range. Some analysts had worried that the price might be too high in a tepid IPO market, but others said the company's history of rapid growth, exclusive products and acquisition potential justified a premium price.

The Chicago Board Options Exchange, based in Chicago, is the country's largest options exchange. It is famous for creating products such as the VIX, a popular gauge of risk known as the market's "fear index."

The shares, trading on the Nasdaq Stock Market under the symbol "CBOE," are rising $4.15, or 14 percent, to $33.15 in morning trading.